Pfizer and BioNTech say their vaccine has been shown to be effective against coronavirus variants that emerged in Britain and South Africa.
They said the virus mutations had only a small impact on the effectiveness of antibodies generated by the vaccine.
Pfizer said it would continue to monitor its “real-world effectiveness” against new strains.
Earlier this week Moderna said its vaccine was also effective against the British variant but gave less protection against the South African one.
It is developing a booster shot to tackle the mutation.